Agriculture requires farmers to obtain sufficient access to water. Water scarcity has become a critical constraint to farming in many parts of the world and shortages of water or drought can adversely affect crop yields. Crop irrigation during periods of low rainfall or drought remains the logical remedy for decreased crop yields and plant death. However, the expense associated with irrigation may be prohibitive and will likely increase as the availability of fresh water declines. Alternatives to irrigation, such as methods that maintain healthy crops during periods of drought, are continuously sought.
Some 2.8 billion people currently live in water-scarce areas. Thus, even in the absence of drought, there is a significant interest in conserving the amount of water that is routinely consumed by plants, including agricultural crops and other plants. For example, a large fully grown tree may evaporate, or “transpire,” several hundred gallons of water through its leaves on a hot, dry day. At least ninety percent of the water that enters a plant's roots is used in this process of transpiration.